Oh? I'm surprised, I think your comment is the first negative opinion on Arcane that I see (to be fair, I wasn't really searching for them either). So I'm curious if you don't mind explaining further, what for example did you find outright bad or making no sense? I would love to hear your opinion, also about season 1 as you specifically mention season 2, was the first better for you? I personally cannot say there was a lot bugging me and usually plotholes or characters acting against their role and background and personality just for the story's sake bother me plenty.
For context, I did know about runeterra and a bit of the stories from before Arcane came out, but I would never consider myself versed in it. I did read some of the background stories officially posted by Riot, some of the comics, and played a bit of league and legends of runeterra, but of course there's not that much story in the games anyway.